Mean Polarizability Research Articles

Relaxation dynamics of l-alanine in water medium investigated by dielectric relaxation spectroscopy.

The complex dielectric permittivity of L-alanine in aqueous medium at different concentrations and different temperatures were measured in the microwave (0.02 < ν/GHz < 20) frequency region by using open-ended coaxial probe technique. From the reflection coefficient and impedance data, the real and imaginary part of the dielectric permittivity values is determined. It is observed that there is a decrease in the real part of the dielectric permittivity up to certain frequency and an increase in the imaginary part of the dielectric permittivity with increase in the molar concentration of L-alanine in water medium. Based on the experimental data the average relaxation time values are calculated and its behavior is analyzed in terms of bound water and free water molecules. The theoretical dipole moment of L-alanine is calculated at gaseous state as well as in aqueous medium by using PCM and IEFPCM model at HF, DFT/B3LYP and MP2 calculations using 6-311G* basis set. Analysis between experimentally determined parameters and computed dipole moments were discussed. The mean molecular polarizability is calculated from the Lippincott δ function potential model and compared with the Le Fèvre method of polarizability values.

Effect of the formation of silver nano‐binuclear complex on the refinement of cytotoxic and antibacterial potency of coumarin Schiff base: Spectroscopy, thermal, X‐ray diffraction analyses and density functional theory calculations

A new Schiff base (SCH) was prepared using 8‐acetyl‐7‐hydroxy‐4‐methylcoumarin and sulfaclozine. Its silver complex was also synthesized. These compounds were subjected to elemental and spectral analyses. The silver complex was also subjected to thermogravimetric analysis, molar conductance measurements, scanning electron microscopy, energy‐dispersive X‐ray analysis and X‐ray diffraction measurements. The formula of the complex was determined as [(Ag2SCH(NO3)2]. The molar conductance indicates its non‐electrolyte character. The electronic structure and nonlinear optical parameters of SCH and its complex were investigated theoretically at the B3LYP/GENECP level. The geometry of the studied complex is non‐planar as indicated from the dihedral angles between central Ag metal ion and coordinated centres of SCH. Density functional theory calculations were also carried out to calculate the global properties of hardness, global softness and electronegativity. The calculated energy gap between HOMO and LUMO energies shows that charge transfer occurs within the studied complex. The total static dipole moment, the mean polarizability, the anisotropy of the polarizability and the mean first‐order hyperpolarizability were calculated and compared with those of urea as a reference material. The results of the mean first‐order hyperpolarizability showed that SCH and its silver complex are excellent candidates as nonlinear optical materials. The compounds were screened for their antimicrobial effect against various species of bacteria and fungi. Their anticancer activities were evaluated in vitro against the human cancer cell line MCF‐7 (human breast adenocarcinoma).

First theoretical study of linear and nonlinear optical properties of diphenyl ferrocenyl butene derivatives

In this work, structure, linear and nonlinear optical (NLO) properties, as well structure–property relationships of fourteen diphenyl ferrocenyl butene compounds (DFB compounds 1–7 (E and Z isomers) have been investigated by ab initio methods and density functional theory (DFT) to evaluate the effects of the basis sets, functionals and electron correlation at the MP2 level. For the linear optical properties, we have been interested on the mean polarizability 〈α〉 and the polarizability anisotropy Δα. For the NLO properties, electric field-induced second harmonic generation (EFISHG) β//(−2ω;ω,ω) and hyper-Rayleigh scattering (HRS) βHRS(−2ω;ω,ω) were investigated. Close structures have been obtained with some DFT functionals for compound 2. NLO calculations reveal that compounds 1 and 2 for both E and Z isomers are a remarkably large βHRS. The results reached from the traditional functionals are in good accordance with those obtained by the corrected functionals. Inverse relationships between the gaps of HOMO–LUMO orbitals and first hyperpolarizabilities have been obtained. Using strong acceptor groups, the results will provide into the electronic properties of this important class of compounds with a promising future.

Synthesis, Antioxidant Activity and Theoretical Investigation of Isoxazolines Derivatives of Monoterpenoids

The 3+2 cycloaddition reactions are important to generate five-membered heterocyclic compounds as well as altering biological activity effects based on structure. In the study, we synthesized new isoxazoline derivatives of different monoterpenoids and examined the structure analysis using spectroscopical analysis methods, reveal changes in the theoretical analysis related to the biological activity. These new compounds exhibit antioxidant activities; DPPH radical scavenging, ferric reducing, metal chelating activities which are significantly higher than the related commercial monoterpenoids. Theoretical approaches on the compounds containing isoxazole moiety have been performed by the DFT/B3LYP/method, 6-31G(d,p) basis set in the ground state. The global and local chemical reactivity properties of the compounds were investigated by considering the values of electronegativity, global hardness-softness, electronic chemical potential, electrophilicity index and condensed Fukui functions, local softness and local electrophilicity index. Furthermore, total energy, FMOs energy values and the dipole moment (&amp;#181;), mean polarizability (&amp;#945;), and first order hyperpolarizability (&amp;#946;) values were analysed at the theoretical level to examine the polarizability characteristics of the compounds. The antioxidant activity values of the newly synthesized compounds were compared with a finding of the computational study. The results obtained exhibited good correlation on some parameters.

Substituent effects on linear and nonlinear optical properties of fluorescent (E)-2-(4-halophenyl)-7-arlstyrylimidazo[1,2-A]pyridine: spectroscopic and computational methods

Abstract Effects of alkylamino and bromo substituents on imidazo[1,2-a]pyridines containing donor-π-acceptor type groups were comprehensively investigated for their linear and nonlinear optical properties by solvatochromic and DFT (CAM-B3LYP and BHandHLYP) methods. The difference between the ground and excited dipole moments as well as their ratios obtained by solvatochromic analysis indicate that the excited state is more polar than the ground state for both the bromo and diethyl amino derivative. More than twofold enhancement in the excited state dipole moments was observed as revealed by the difference and ratio of dipole moment upon the introduction of alkylamino donor group and these suggest large intramolecular charge transfer in the dyes. Stabilization energy above 20 kJ/mol was observed for large number of electron donor–acceptor interactions in Natural Bonding Orbital (NBO) analysis. Bond length alternation (BLA) and Bond order alternation (BOA) values tend to zero suggesting a high degree of polarization in the dyes. Enhancement in mean polarizability (α0), first hyperpolarizability (β0) and second static hyperpolarizabilities ( $\bar \gamma$) were observed by the introduction of alkylamino and bromo group in place of chloro in spite of the fact that Hammett constant of chloro and bromo are the same. The dyes have fundamental and intrinsic properties within the Hamiltonian limits. The two-photon absorption cross section value (≈100 GM) is comparable with LDS-698, a commercial TPA dye. This investigation is important for understanding the electronic structure of imidazo[1,2-a]pyridine with active functional groups and extending the potential for optical applications.

5-Phenyl thiophene amino phenol derivatives: Synthesis, spectroscopic characterization, computational study and antimicrobial activity

(((5-phenylthiophen-2-yl) methylene) amino) phenol derivatives were synthezised and characterized by IR and NMR. The density functional theory (DFT) method with 6–311++G (d,p) basis set was used for both calculations of molecular geometries and spectroscopic parameters. Frontier molecular orbitals and molecular electrostatic potential maps for compounds 1a, 1b and 1c were obtained. Due to the differences observed in the theoretical spectral parameters, NH⋯O type intermolecular/intramolecular hydrogen bonds in the molecular structures of compounds were proposed. To determine the nonlinear optical properties of compounds, the mean polarizability (α) and the first hyperpolarizability (β) obtained as 44.2388 × 10−24 esu and 373.1267 × 10−31 esu for compound 1a, 43.8141 × 10−24 esu and 195.2893 × 10−31 esu for compound 1b, 36.9489 × 10−24 esu and 120.73825 × 10−31 esu for compound 1c, respectively were used. These values indicate that compounds can be suggested as a good nonlinear optical material. In addition, the antimicrobial properties of compounds were investigated by considering antileishmanial and antibacterial activities. The compounds were evaluated against Leishmania infantum promastigots for antileishmanial activity and against five standard bacteria (Escherichia coli, Shigella flexneri, Yersinia enterocolitica, Salmonella typhimurium and Salmonella enterica) for antibacterial activity, by microdilution broth assay with Alamar Blue Dye. Results show that only compound 1a has high antileishmanial activity and can be evaluated in leishmaniasis treatment after in vivo studies and also considered in pharmacological studies for antibacterial activity.

Distributed polarizability of fullerene [2+1]-adducts C60Xn (n = 1 and 2) with symmetric addends X = CH2 and O: A fresh view on the effect of positional isomerism

We have performed a site-specific analysis of the mean polarizability of fullerene [2+1]-adducts C60Xn (n = 1 and 2) with symmetric addends X = CH2 and O using the distributed polarizability model. We have found that the contributions from the fullerene core and addends to the molecular polarizability are not the same for different regioisomeric C60X2: the core contribution linearly decreases and the addend contribution linearly increases with the distance between the addends (or the functionalized bonds of the C60 cage). Additionally, the contributions are sensible to the degree of the fullerene core functionalization: the contribution of the C60 core decreases with the number of the attached addends due to reducing its π-electronic system.

2‐(1,1‐dioxidobenzo[b]thiophen‐3(2H)‐ylidene)malononitrile (BTD) Based Styryl Chromophores‐ Solvatochomic and Computational Investigation of Linear and NLO properties

AbstractLinear and nonlinear optical properties of the twelve styryl dyes are investigated using density functional theory (DFT). Range‐separated hybrid CAM−B3LYP and global hybrid BHandHLYP estimate high second order hyperpolarizability. Mean polarizability (α0), polarizability anisotropy (Δα), static first‐order hyperpolarizability (β0) and second hyperpolarizability (γ) were found to be overestimated in CAM−B3LYP than in BHandHLYP. As bond length alternation (BLA) increases first order hyperpolarizability increases. Multilinear regression analysis (MLR) shows the solvent basicity, polarizability and dipolarizabilty are responsible for absorption solvatochromism. The ratio of the dipole moments increases as donor strength and conjugation increases which support charge transfer. The figure of merit (FOM) and intrinsic hyperpolarizability found more in chromophores with dialkylamine donors. As the stability indicated by electrophilicity indices decreases the hyperpolarizability increases. Interrelationships between α0, β0 and γ were evaluated and it shows good linear fit. Absorption is red shifted and hyperpolarizability increases with the amplitude of the sine‐shaped potential along the conjugation chain. A high molecular electrostatic potential was observed in dyes containing 2‐piperidinothiophene donor.

Computational study of new 1,2,3-triazole derivative of lithocholic acid: Structural aspects, non-linear optical properties and molecular docking studies as potential PTP 1B enzyme inhibitor

We have reported synthesis of a novel 1,2,3-triazole conjugate of lithocholic acid by 1,3-dipolar cycloaddition reaction. The molecular properties such as geometry, conformations, bond lengths and dihedral angles were investigated theoretically. The bond order analysis was performed using Wiberg bond order (WBO), Fuzzy bond order (FBO) and Laplacian bond order (MBO) method. Electronic properties of molecule such as electrostatic surface potential analysis, frontier molecular orbital analysis, reduced density gradient, total density of states, and global chemical reactivity indices have been investigated. The nonlinear optical properties were also investigated. Total dipole moment, mean polarizability and hyperpolarizability were found to be much higher than standard urea molecule which suggests that it could act as potential NLO material. The molecular docking calculations are also performed to investigate its potential as PTP 1B enzyme inhibitor.

Exploring the role of quantum‐mechanical descriptors in the concentration‐dependent adsorption of aromatic organic compounds by multiwalled carbon nanotubes

AbstractAn accurate quantitative prediction for concentration‐dependent adsorption of organic compounds by carbon‐nanotubes (CNTs) is increasingly in demand to evaluate not only their applications but also risk associated using CNTs. This is often carried out using poly‐parameter linear‐solvation‐energy‐relationships (pp‐LSERs) based on adsorbate descriptors. This work examines the predictivity of existing pp‐LSERs in the prediction of adsorption of aromatic organic compounds by multi‐walled CNTs (MWCNTs) at five different adsorbate concentrations, and compares that with the predictivity of quantum‐mechanical models while revealing an essential role of electron‐correlation. Notably, the most influencing descriptor for the adsorption was found to be the mean polarizability but that arising from the quantum‐mechanical exchange interactions between electrons of the same spin. This work also proposes reliable predictive models based on a combination of the quantum‐mechanical descriptors and pp‐LSER's descriptors, which were applied to predict the adsorption of nucleobases and steroid hormones, with Progesterone found to be maximally adsorbed.

Exaltation of polarizability as a common property of fullerene dimers with diverse intercage bridges

ABSTRACTIn the present work, polarizability of 34 C60 fullerene dimers with different bridges between the cages has been studied by the PBE/3ζ density functional theory method and relevant additive scheme. All studied compounds reveal the exaltation polarizability Δα (positive deviation of the DFT-calculated mean polarizability from the additive value), which was previously found for the fullerene dimers with the direct linkage of the fullerene moieties, so it is a common property of fullerene dimers regardless of their chemical nature. The Δα values depend on intercage distance L and the type of the bridging group and almost independent of topological features of the structures.

Concentration dependent adsorption of aromatic organic compounds by SWCNTs: Quantum-mechanical descriptors for nano-toxicological studies of biomolecules and agrochemicals

For evaluating the environmental risk associated using carbon nanotubes (CNTs), a successful prediction is desired for the adsorption of organic compounds (OCs) by CNTs at different adsorbate concentrations. This is most often achieved through poly-parameter linear solvation energy relationships (LSERs) based on solvatochromic descriptors. This study examines the real predictivity of the existing LSERs for predicting the adsorption of OCs by single-walled CNTs (SWCNTs) while comparing it with that of the models developed in the present work using quantum-mechanical descriptors. The real predictivity of the quantum-mechanical models and existing LSERs is compared using state-of-the-art statistical procedures employing an external prediction set of compounds not used in the model development. The quantum-mechanically computed mean polarizability, but originating from the interactions between electrons of parallel spin, is found to play an essential role in the adsorption of OCs by SWCNTs. Besides the solvatochromic descriptors (McGowan volume and molar excess refractivity), the instantaneous inter-electronic interactions, captured through electron-correlation based quantum-mechanical descriptors, are found to significantly affect the adsorption at varying adsorbate concentration. The models developed using a combination of quantum-mechanical and solvatochromic descriptors are found to be quite reliable. The models proposed were further employed to predict the adsorption of agrochemicals such as insecticides, pesticides, herbicides, as well as adsorption of endocrine disruptors and biomolecules such as nucleobases and steroid hormones. These are predicted to be strongly adsorbed by SWCNTs with Progesterone and Guanine exhibiting maximal interaction with the SWCNTs among biomolecules. The quantum-mechanical descriptors proposed in this work can be used for the risk assessment of SWCNTs in systems where adsorption is the primary process.

An old oxovanadium(IV) complex of N-(salicylidene)sulfanilamide: theoretical validity of experimental observations

Sulfa drug Schiff base complexes of oxovanadium are counted among highly significant molecular scaffolds of industrial and medicinal relevance. In order to present a theoretical validation of our earlier reported complex of this sort herein, a comparative experimental theoretical investigation of N-(salicylidene)sulfanilamide Schiff base and its oxovanadium(IV) complex, [VO(sal-snm)2(H2O)] based on density functional theory calculations using the B3LYP as functional and 6-31++G(d,p) (for ligand)/LANL2DZ (for Vanadium) basis set is being reported. The calculated vibrational frequencies have been compared with experimental FT-IR spectra of the selected compounds. The Molecular geometry optimizations, frontier orbital analysis, hyperpolarizability calculations and molecular electrostatic surface potential (MESP) topologies of the title compounds have been sought in this work. From the molecular geometrical optimization of the oxovanadium(IV) complex a suitable octahedral structure has been confirmed. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecules. The Non-linear optical properties encompassing the applicability of electric dipole moment (μ), polarizability (α), mean polarizability (Δα) and hyperpolarizability (β0) values have been evaluated through quantum chemical calculations.

Preparation and spectroscopic properties, density functional theory calculations and nonlinear optical properties of poly (acrylic acid-co-acrylamide)-graft-polyaniline

Poly (acrylic acid-co-acrylamide)-graft-Polyaniline was synthesized via chemical oxidation polymerization using ammonium persulphate as initiator at 40 °C under N2 atmosphere. The prepared poly (acrylic acid-co-acrylamide)-graft-Polyaniline was characterized by different analytical tools. The apparent activation energy of grafting reaction was calculated and found to be 48.7753 kJ/mol. Also, ΔH*and ΔS* as thermodynamic parameters for activation were calculated which equal to 46.4300 k J/mol. and −14.0379 J/mol. K respectively. The optimized structures of the graft (one, two and three units or ( monomer, dimer and trimer) were theoretically investigated at the B3LYP/6-311G level. The geometry of the graft are non-planar as indicated from the values of dihedral angles. The global properties of hardness, global softness and electronegativity were calculated. The calculated small energy gap between highest occupied and lowest unoccupied molecular orbital energies shows that charge transfer occurs within the graft compound. The molecular electrostatic potential for the graft was investigated. The obtained total static dipole moment, mean polarizability, anisotropy of polarizability and mean first-order hyperpolarizability (<β>) were compared with those of urea as a reference material. The results for <β> showed that the graft is excellent candidates as nonlinear optical materials.

Spectroscopic characterization and density functional studies of new thiadiazole 1,1-dioxide compounds

New thiadiazole compounds, 3-imino-4-(anthracene-9-yl)-1,2,5-thiadiazolidine 1,1-dioxide (I) and 3-imino-4-(10-chloroanthracene-9-yl)-1,2,5-thiadiazolidine 1,1-dioxide (II) were synthesized and characterized by Fourier Transform Infrared Spectroscopy (FTIR), 13C and 1H NMR and UV–vis spectroscopic methods. Calculations of molecular geometries and spectroscopic parameters were performed using DFT/6–311++G(d,p) method. Frontier Molecular Orbitals (FMOs), Non-Linear Optical (NLO) properties and Molecular Electrostatic Potential (MEP) maps of newly synthesised compounds were obtained. The some considerable differences between experimental and calculated vibrational frequencies and NMR chemical shift values can be attributed to the presence of NH⋯O type intermolecular hydrogen bonds in the molecular structures of both compounds. NLO properties of compounds were determined by using the mean polarizability (α) and the first-order hyperpolarizability (β) values calculated as 36.8326 × 10−24/18.7571 × 10−31 esu for I, 36.9489 × 10−24/31.6544 × 10−31 esu for II, respectively at the mentioned computational level. These values are greater than the ones of urea (α = 4.9067 × 10−24 and β = 7.8782 × 10−31 esu) and therefore, NLO properties study demonstrates that the both compounds, especially compound II, can be suggested as a good nonlinear optical material.

Experimental (FT-IR, Raman and NMR) and Theoretical (B3LYP, B3PW91, M06-2X and CAM-B3LYP) Analyses of PTert-Butylphenyl Salicylate

The spectroscopic investigations of p-tert-butylphenyl salicylate (C17H18O3) molecule were performed using 13C and 1H NMR chemical shifts, FT-IR and Raman spectroscopies. Molecular geometric optimizations, vibrational frequencies, Carbon-13 and Proton NMR chemical shifts (in vacuum and chloroform), HOMO-LUMO properties, natural bond orbital (NBO) analysis, nonlinear optical properties and thermodynamic parameters of p-tert-butylphenyl salicylate molecule was studied using B3LYP, B3PW91, M06-2X and CAM-B3LYP functionals in DFT method at the 6-311++G(d,p) basis set. NBO analysis was carried out to investigate the intramolecular hyrogen bonding (O-H...O) in the title molecule. Some of the molecular properties such as ionization potential (I), electron affinity (A), chemical hardness (h), chemical softness (z), electronegativity (χ), chemical potential (μ) and electrophilicity index (w) parameters were determined via HOMO and LUMO energies of the title molecule. Also, quantum chemical computations were performed to determine the dipole moment (µtotal), mean polarizability (α), anisotropy of the polarizability (∆α) and first hyperpolarizability (β0) values. Thermochemical properties of the title molecule were investigated with the aforementioned calculation levels. The recorded experimental spectroscopic results were found to be in good agreement with the computed data.

Polarizability of the Si60H60 Derivatives Containing Epoxide Moieties (Si60H60−2nOn with n up to 30): A DFT Study

We have applied density functional theory calculations to study polarizability of the Si60H60 derivatives with epoxide moieties (Si60H60−2nOn with n up to 30). The results show that mean polarizability, α, of oxygen-containing silicon fullerene derivatives is higher than that of Si60H60. The mean polarizabilities of the isomers slightly depend on the positional relationship of the epoxide moieties, and are determined mainly by the number of epoxide moieties. Mean polarizabilities of Si60H60−2nOn linearly increase with n, and are characterized by the depression of polarizability. The formula describing the mean polarizability as a function of the number of epoxide groups has been obtained, which may be important for the design of silicon-containing nanostructures with regulated polar parameters.

Polarizability tensor invariants of H2, HD, and D2.

We report an exhaustive compilation of wavelength-dependent matrix elements over the mean polarizability (α¯) and polarizability anisotropy (γ) operators for the rovibrational states of the H2, HD, and D2 molecules together with an accompanying computer program for their evaluation. The matrix elements can be readily evaluated using the provided codes for rovibrational states with J = 0-15 and v = 0-4 and for any laser wavelengths in the interval 182.25-1320.6 nm corresponding to popular, commercially available lasers. The presented results substantially extend the scope of the data available in the literature, both in respect of the rovibrational transitions analyzed and the range of covered laser frequencies. The presented detailed tabulation of accurate polarizability tensor invariants is essential for successful realization of our main long-term goal: developing a universal standard for determining absolute Raman cross sections and absolute Raman intensities in experimental Rayleigh and Raman scattering studies of molecules.

Nature of bonding and cooperativity in linear DMSO clusters: A DFT, AIM and NCI analysis

This study aims to cast light on the nature of interactions and cooperativity that exists in linear dimethyl sulfoxide (DMSO) clusters using dispersion corrected density functional theory. In the linear DMSO, DMSO molecules in the middle of the clusters are bound strongly than at the terminal. The plot of the total binding energy of the clusters vs the cluster size and mean polarizabilities vs cluster size shows an excellent linearity demonstrating the presence of cooperativity effect. The computed incremental binding energy of the clusters remains nearly constant, implying that DMSO addition at the terminal site can happen to form an infinite chain. In the linear clusters, two σ-hole at the terminal DMSO molecules were found and the value on it was found to increase with the increase in cluster size. The quantum theory of atoms in molecules topography shows the existence of hydrogen and SO⋯S type in linear tetramer and larger clusters. In the dimer and trimer SO⋯OS type of interaction exists. In 2D non-covalent interactions plot, additional peaks in the regions which contribute to the stabilization of the clusters were observed and it splits in the trimer and intensifies in the larger clusters. In the trimer and larger clusters in addition to the blue patches due to hydrogen bonds, additional, light blue patches were seen between the hydrogen atom of the methyl groups and the sulphur atom of the nearby DMSO molecule. Thus, in addition to the strong H-bonds, strong electrostatic interactions between the sulphur atom and methyl hydrogens exists in the linear clusters.

Evolution of the Complex Refractive Index of Secondary Organic Aerosols during Atmospheric Aging

The wavelength-dependence of the complex refractive indices (RI) in the visible spectral range of secondary organic aerosols (SOA) are rarely studied, and the evolution of the RI with atmospheric aging is largely unknown. In this study, we applied a novel white light-broadband cavity enhanced spectroscopy to measure the changes in the RI (400-650 nm) of β-pinene and p-xylene SOA produced and aged in an oxidation flow reactor, simulating daytime aging under NO x-free conditions. It was found that these SOA are not absorbing in the visible range, and that the real part of the RI, n, shows a slight spectral dependence in the visible range. With increased OH exposure, n first increased and then decreased, possibly due to an increase in aerosol density and chemical mean polarizability for SOA produced at low OH exposures, and a decrease in chemical mean polarizability for SOA produced at high OH exposures, respectively. A simple radiative forcing calculation suggests that atmospheric aging can introduce more than 40% uncertainty due to the changes in the RI for aged SOA.